RU2379138C1 - Method of logitudinal separation of rolling metal - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes heating of metal, pre-forming of consisting of connected to each other by jumper parts of profile and separation of received profile for parts by destruction of connecting jumper by means of nonpowered division device. Optimal conditions for providing of directional stability of strip at its division are provided ensured by that at distraction of jumper axle base between rolls forming coupled profile, and rollers of nonpowered division device should not exceed value regulated by mathematical dependence.

EFFECT: reduction of discard and power inputs connected to division of rolling metal, reduction of wear of equipment at manufacturing of symmetrical and non-symmetrical profiles.

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Description

The invention relates to the field of ferrous metallurgy, namely to rolling production, and can be used in the production of symmetric and asymmetric profiles.

A known method for the longitudinal separation of articulated profiles, including the formation of an articulated profile with its simultaneous separation in the deformation zone of the rolling stand (VP Slednev, Paired rolling of high-quality profiles. M .: Metallurgy, 1988, pp. 10-11).

The simultaneous execution of the operations of forming an articulated profile and longitudinal separation in the rolls of the rolling stand seriously complicates the setup of the equipment and, as a result, leads to a violation of the stability of the longitudinal separation, marriage, emergency situations, the formation of a burr at the interface, which is additionally promoted by the high ductility of the metal in the hot state.

The closest is the method of longitudinal separation of rolled products in the mill stream, in which an articulated profile is formed in the rolls of the rolling stand, and longitudinal separation occurs in a non-driven dividing device located next to the rolling stand (RU No. 2201816, B21B 1/02, 2003).

The disadvantage of this separation method is the possibility of losing the longitudinal stability of the strip in the gap between the line connecting the centers of the rolls forming an articulated profile and the axis of the rollers of the non-driven dividing device. The loss of stability is the cause of both the impossibility of longitudinal separation in the non-driven dividing device with the creation of incidents (if there are no guides between the rollers and the dividing device, then with the loss of longitudinal stability the profile is formed in this interval, which leads to serious damage to the equipment), and increased wear of the equipment, defects in the surface of the finished product (defective), additional energy costs (if rails are installed between the rollers and the non-drive dividing device, then if the longitudinal stability is lost, the strip will rub heavily on the guides, which will lead to their rapid wear, the formation of scratches on the strip surface, and additional power consumption for overcoming friction forces).

The objective of the invention is to provide longitudinal stability of the strip during separation, reducing the marriage associated with the separation, reducing wear and tear of equipment and reducing energy costs for separation.

The problem is achieved in that in the known method of longitudinal separation of rolled products after heating the metal and pre-forming consisting of several parts of the profile interconnected by a jumper, comprising dividing the profile into parts by destroying the jumper with an non-driven roller dividing device, according to the invention, the non-driven roller dividing device is installed at a distance not exceeding the center distance between the rollers forming an articulated profile and the rollers not driven a divider, which is defined by the following relationship:

where l _max - the maximum center distance between the rollers forming an articulated profile, and the rollers of the non-driven dividing device, mm;

E is the modulus of elasticity of the material of the shared strip, MPa;

i ² _min is the minimum radius of inertia, mm ² ;

σ _p is the back pressure required for longitudinal separation, MPa;

σ _s is the actual deformation resistance of the shared material, MPa;

k = 0.5 is the coefficient of reduction of length.

The technical essence of the invention is to create optimal conditions for ensuring the longitudinal stability of the strip when it is separated using a non-driven roller dividing device, which is installed at a distance not exceeding the axle distance between the rollers forming an articulated profile and the rollers of the non-driven dividing device. The maximum center distance is determined by the dependence:

for σ _p ≤σ _s ,

where l _max - the maximum center distance between the rollers forming an articulated profile, and the rollers of the non-driven dividing device, mm;

E is the modulus of elasticity of the material of the shared strip, MPa;

i ² _min is the minimum radius of inertia, mm;

σ _p is the back pressure required for longitudinal separation, MPa;

σ _s is the actual deformation resistance of the shared material, MPa;

k = 0.5 is the coefficient of reduction of length.

Failure to comply with the stipulated condition will lead to a loss of the longitudinal stability of the strip in the gap exceeding the maximum center distance between the rollers forming the articulated profile and the rollers of the non-driven dividing device. Loss of stability will be the cause of incidents, product defects, depreciation or destruction of equipment, additional energy costs for separation.

The proposed method is illustrated in the drawing, which shows a diagram of the longitudinal separation of hire. The diagram shows rolls 1 forming an articulated profile 2 with rollers 3 of a non-drive dividing device located behind them. In the rollers 3 non-power dividing device is the separation of the articulated profile 2 into strips 4.

The method is carried out through the use of reserve friction forces in the deformation zone of the rolling stand, forming an articulated profile, behind which a non-drive dividing device is installed. The reserve frictional forces create a backwater pressure, due to which there is a longitudinal separation in the non-driven dividing device. The maximum center distance between the rollers forming an articulated profile and the rollers of a non-driven dividing device can be determined on the basis of the following considerations. We use the well-known Euler formula to determine the critical force at which the rod loses stability (Feodosiev V.I. Material resistance. M: Nauka, 1986, p. 425):

where P _cr - critical force, N;

E is the modulus of elasticity, MPa;

J _min is the minimum moment of inertia, mm ⁴ ;

k is the coefficient of reduction of length;

l - rod length, mm.

Consider a part of the strip with a length equal to the center distance between the rollers forming the articulated profile and the rollers of the non-drive dividing device, as a rod loaded with a force equal to the force required for longitudinal separation. Using the dependence (2), we obtain:

where l _max - the maximum center distance between the rollers forming an articulated profile, and the rollers of the non-driven dividing device, mm;

Q is the longitudinal force required for separation in a non-driven dividing device, MPa.

We pass from the force Q to the back pressure σ _p , which provides longitudinal separation:

where F is the cross-sectional area of the articulated strip, mm ² ;

σ _p is the back pressure required for longitudinal separation, MPa.

Considering that the ratio J _min / F, in the course of resistance of materials is called the radius of inertia (i ² _min ), we transform (4) to the form:

The resulting dependence (5) is applicable provided:

where σ _s is the actual deformation resistance of the shared material, MPa.

If condition (6) is not met, a section of the strip with a length equal to the interaxal distance between the rollers forming the articulated profile and the rollers of the non-drive dividing device begins to plastically deform, the cross-sectional area increases, and the process of longitudinal separation becomes unpredictable.

Example: Consider the case of a longitudinal separation of an articulated strip into a non-drive dividing device into two parts. Baseline:

width 25 mm, height 10 mm (the small size of the shared profile is due to the fact that separation is usually carried out at the final stage of rolling in the finishing stands when receiving small reinforcing profiles from No. 8 to No. 14), the thickness of the lintel is 5 mm, the diameter of the dividing rollers is 100 mm . The value of the back-up voltage required for separation, depending on the separation method used (breaking, crushing, cutting the connecting jumper), can be found experimentally or analytically. For clarity, we consider an analytical approach in determining the desired voltage when cutting by non-drive circular knives, placed in a non-drive dividing device. We use the dependence given in the work (Tselikov A.I., Polukhin P.I., Grebennik V.M. et al. Machines and assemblies of metallurgical plants, vol. 3. M .: Metallurgy, 1981, p. 365), for determination of cutting force:

where k ₁ - coefficient taking into account the hardness of the metal being cut (k ₁ = 0.6 ... 0.75);

k ₂ - coefficient taking into account the increase in cutting force during blunting of knives (k ₂ = 1.2 ... 1.3);

k ₃ - coefficient taking into account the increase in lateral clearance between circular knives during their long-term use (k ₃ = 1,1 ... 1,2);

h _lane - the thickness of the shared jumper, mm;

ε _n - shear coefficient;

α _p - angle of cut, deg.

The longitudinal force required for separation by cutting can be determined by the formula:

Using the dependencies (7) and (8), we find the back pressure required for cutting separation:

where n _lane - the number of shared jumpers. Using dependences (5) and (9), as well as the initial dimensions of the double strip, we determine the maximum distance l _max when the strip is cut from 09G2 steel, at a temperature of 1050 ° C and a process speed of 10 m / s.

To find the deformation resistance (σ _s ) and elastic modulus (E), we will use the dependences given in (Komratov Yu.S., Lekhov O.S. Investigation of the process of rolling I-beams in a crimping stand 1300 UBS. Steel No. 10, p. 57 -59, 2007):

where U _cp is the strain rate, s ^-1 ;

ε is the degree of deformation,%;

t is the temperature of the workpiece, ° C.

Find the strain rate in the section zone according to the formula:

where v is the speed of the separation process, mm / s;

Δh is the absolute deformation of the bridge, mm;

r _p is the radius of the dividing roller, mm

Define the deformation resistance and the elastic modulus of the shared workpiece

σ _s = 288 · 447 ^0.107 (ln50) ^1.45 2.74 ^{-0.00235 · 1050} = 334 MPa;

E = -4.566 × 10 ⁵ + 1050 + 160 · 3,266 · 10 ^8/1050 = 22448 MPa.

We calculate the backwater voltage required to separate the jumper:

Define the radius of inertia:

where b, h is the width and height of the shared strip, mm

Determine the maximum center distance between the rollers forming an articulated profile and the rollers of the non-drive dividing device with a coefficient of reduction of length 0.5 in accordance with the conditions considered in the example and according to the recommendations of the work (Feodosiev V.I. Material resistance. M .: Nauka, 1986, p. 425).

for σ _p ≤σ _s ,

Thus, the maximum center distance between the rollers forming an articulated profile and the rollers of a non-driven dividing device, guaranteeing longitudinal stability, should not exceed 637 mm under the considered conditions. When changing the conditions of longitudinal separation, the value of l _max will change. For example, under the conditions under consideration, the separation of a built-up strip (there are cases of simultaneous separation of up to five bands), that is, at the same time two jumpers, the value of l _max will be:

for σ _p ≤σ _s ,

When using a different separation method, based on breaking or crushing the jumper, the value of l _max will be different (even less, since these separation methods are possible with large values of the back pressure σ _p ).

Using the proposed method in comparison with the existing allows you to get the following advantages:

- reduce accident rate and the number of defects during the implementation of the rolling process - separation;

- reduce wear and improve working conditions of equipment used for longitudinal separation;

- reduce energy costs for the process of longitudinal separation.

Claims (1)

A method for longitudinally separating rolled metal after heating the metal and pre-forming a section of several profile parts connected by a jumper, comprising dividing the profile into parts by destroying the connecting bridge by a non-driven roller dividing device, characterized in that the non-driven roller dividing device is installed at a distance not exceeding the center distance between rollers forming an articulated profile and rollers of a non-driven dividing device, which op edelyayut by the following relationship:

for σ _p ≤σ _s ,
where l _max - the maximum center distance between the rollers forming an articulated profile, and the rollers of the non-driven dividing device, mm;
E is the modulus of elasticity of the material of the shared strip, MPa;
i ² _min is the minimum radius of inertia, mm;
σ _p is the back pressure required for longitudinal separation, MPa;
k = 0.5 is the coefficient of reduction of length;
σ _s - the actual resistance to deformation of the shared material, MPa.

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